A sale of second-hand Apple laptops costing only $50 have caused a near riot in Virginia in the US.

More than 5,500 people queued for a chance to buy one of the 1,000 laptops and stampeded when the sale of the computers started.

In the crush 17 people were injured and four needed hospital treatment.

The four-year-old iBooks were being sold off cheap because Henrico County switched from Apple to Dell to supply laptops for its schools.

Riot gear

People began queuing at the Richmond International Raceway in Henrico County, Virginia shortly after midnight for the start of the 16 August sale.

The sale was due to begin at 9am local time, but as the queue grew to almost a kilometre in length, organisers brought forward the start time by two hours.

Eyewitnesses described the scene as terrifying and chaotic

When the gates opened, a stampede started as people raced to be at the head of the queue for the cheap iBooks.

In the crush, people were trampled on, a chair was thrown, an elderly man was pushed to the ground, a baby's buggy was crushed and one desperate buyer tried to drive his car through the crowd.

Eyewitnesses described the scene as "terrifying" and "total, total chaos".

Despite a heavy police presence, there were no arrests.

"It's rather strange that we would have such a tremendous response for the purchase of a laptop computer, and laptop computers that probably have less-than- desirable attributes," said Paul Proto, director of general services for Henrico County commenting on the sale of the four-year-old machines.

County officials said they would review events and see what could be done differently for future sales.